Patent document 1 discloses a grooving tool as an example of cutting inserts usable for a grooving process or the like. As shown in FIGS. 14 to 16 of Patent document 1, the grooving tool is provided with a plurality of breaker projections, and the height of these breaker projections is increased stepwise as departing from an end flank surface. Specifically, the grooving tool described in Patent document 1 includes the first stage projection, the second stage projection, and the third stage projection that are sequentially located apart from the end flank surface. The height of these projections is increased stepwise.
However, when chips generated by the foregoing grooving tool climb over the first stage projection and the second stage projection, a rearward flow of the chips may be blocked by the collision of the chips with the third stage projection blocks. Consequently, the chips may stay between the first stage projection, the second stage projection, and the third stage projection. This is because the third stage projection is located behind the first stage projection and the second stage projection and has a larger height than these two projections.
Hence, there has been a need for excellent chip discharge performance in the cutting insert usable for the grooving process or the like.    Patent Document 1: Japanese Unexamined Patent Publication No. 2006-150584